A flat part for a knitting machine and a knitting machine comprising such flat part

ABSTRACT

A flat part for a knitting machine includes a main flat body and a pair of springs protruding on opposed sides of the main flat body and resting against opposed surfaces of a respective groove in the needle-holding cylinder of a knitting machine. Each spring, when the flat part is inserted into the groove, pushes against the respective surface of the groove, so as to make it easier for the flat part to oscillate in the groove and/or to stabilize the positioning of the flat part in the groove.

FIELD OF THE INVENTION

The present invention relates to a flat part for a knitting machine and to a knitting machine, preferably a circular knitting machine, comprising such flat part. The present invention relates to movable flat parts of knitting machines which, when inserted into respective groove, help with their movement stitch formation as carried out directly by the needles which said flat parts or directly or indirectly connected to. In particular, though not necessarily, the present invention relates to the structure of flat parts which, in a circular knitting machine, actuate the needles and turn a relative rotational movement between a needle-holding element and actuating cams into axial movements of said needles.

BACKGROUND OF THE INVENTION

As is known, circular knitting machines comprise a needle-holding element (needle cylinder and/or plate) on which one or more series of needles are arranged in respective grooves along a circular path (circular needlebeds), and devices apt to control the movement of the needles for knitted fabric formation. The devices for controlling the needles of the needle-holding cylinder comprise actuating cams arranged around the cylinder itself, and drive chains configured for operatively connecting the cams to the needles. Each of such drive chains, also known as “catenaries”, comprises several flat parts inserted into each groove and below each needle. Drive chains exhibit butts configured for cooperating with the actuating cams.

It is known to brake or stabilize at least some of the flat parts in the respective grooves by means of suitable braking/stabilizing systems, so as to avoid vibrations thereof during their movements. To this purpose, it is known for instance to bend laterally the flat part so that it is then elastically deformed when inserted into the groove and pushes against opposed lateral surfaces of said groove. It is also known to place an elastic plate on one of the two opposed sides of the flat part so that, when the flat part is inserted into the groove, the elastic plate rests against one of the lateral surfaces pushing the flat part against the opposed lateral surface. It is also known about flat parts which work by oscillating in the respective groove.

For instance, documents WO2018/197970 and WO2018/197971, issued to the same Applicant, disclose for each needle a drive chain comprising a sub-needle slidingly arranged below the respective needle. The sub-needle exhibits a butt moving radially between an operating position, in which it is extracted so as to engage with respective first paths defined by first actuating cams and cause the activation of the needle and the stitch formation, and a non-operating position, in which it is retracted so as not to engage with said first paths. A selector is arranged under the sub-needle and a punch is arranged between the sub-needle and the selector. An activating element is slidingly arranged in the respective longitudinal groove between the sub-needle and the selector, can be longitudinally moved with respect to the punch and with respect to the sub-needle and can be operatively engaged with the sub-needle so as to switch the butt of the sub-needle into and retain it in the respective operating position. The selector comprises an axially moving element slidingly arranged in the respective longitudinal groove below the punch, and an axially stationary element which can be engaged by the selecting device. The axially stationary element oscillates by effect of the selecting device.

SUMMARY

In the framework of flat parts for knitting machines, in particular for circular knitting machines as the ones disclosed above, the Applicant has identified the presence of some drawbacks.

First of all, the Applicant has found out that in known braking/stabilizing systems as those described above, both concerning the lateral plate and the deformation of the whole flat part, the asymmetry of the flat part leads to an asymmetrical positioning of the latter in the respective groove, which can produce asymmetrical, inaccurate movements and unwanted frictions, resulting in a fast wear and requiring frequent maintenance and/or replacement of the flat parts.

Moreover, the Applicant has found out that known braking/stabilizing systems do not allow to adjust the braking force accurately since, in case a single elastic plate is used, a whole side of the flat part rests against the lateral surface of the groove, and conversely, if the whole flat part is bent laterally, the resting points are offset.

The Applicant has also found out that, if the flat part should be able to oscillate, such oscillating movement is not very accurate since it is hindered by several elements/areas of the flat part resting against the lateral surfaces of the groove.

The Applicant has also found out that known machines as described above, in particular those disclosed in WO2018/197970 and WO2018/197971, have a large number of components for each drive chain.

WO2018/197970 and WO2018/197971 exhibit, beyond the needle, four other elements with the respective butts. As a result, also the cams for said butts should be in a large number and therefore complex. The complexity of drive chains leads to high manufacturing, operating and maintenance costs involving the whole machine.

Furthermore, the Applicant has found out that, in the machines described in WO2018/197970 and WO2018/197971, the radial movement of the butt of the sub-needle is related to the axial travel range of the activating element. The axial movements that can be assigned to the needles and sub-needles are therefore limited by the maximum axial travel range of the activating element.

Under these circumstances, an aim underlying the present invention, in its various aspects and/or embodiment, consists in proposing a flat part that is housed in the respective groove so as to provide the correct braking and/or stability during its movements, both oscillating and translational and rototranslational.

An aim underlying the present invention therefore consists in improving the accuracy with which the flat part is moved and/or positioned during the various processing steps of the machine.

An aim underlying the present invention also consists in proposing a flat part that allows to manage/adjust the friction/braking force arising between the latter and the groove in which it is housed.

Moreover, an aim underlying the present inventions consists in proposing a flat part that can be accurately positioned in the groove, in particular so that it lies at a correct distance from the opposed lateral surfaces thereof.

An aim of the present invention also consists in proposing a circular knitting machine which, with the same textile features that can be achieved or even with more textile features that can be achieved with respect to prior art machines, is structurally simpler and more rational, cheaper to be produced and maintained and thus also more reliable.

A further aim of the present invention consists in proposing a circular knitting machine and a method for moving needles which allow to increase the plurality of movements which can be assigned to the needles so as to achieve a higher production flexibility, i.e. so as to manufacture different types of fabrics with several characteristics differing one from the other.

A particular aim of the present inventions consists in proposing a circular knitting machine and a method for moving needles which allow to increase the axial travel ranges of the needles with the same diameter of the needle-holding cylinder.

These and other possible aims, which shall appear better from the following description, are basically achieved by a flat part for a knitting machine, by a drive chain for a needle of a knitting machine, in particular of a circular knitting machine, by a knitting machine, in particular a circular kitting machine, comprising such flat part, according to one or more of the appended claims and according to the following aspects and/or embodiments, variously combined, possibly also with the aforesaid claims.

In the present description and in the appended claims, the words “upper”, “lower”, “above” and “below” relate to the positioning of the machine during normal operation with the central axis of rotation of the needle-holding cylinder in vertical position and the cylinder needles pointing upwards. In the present description and in the appended claims, the words “axial”, “circumferential”, “radial” relate to said central axis.

Some aspects of the invention are listed below.

In one independent aspect, the invention relates to a flat part for a knitting machine, optionally a circular knitting machine, wherein the knitting machine comprises a plurality of grooves, each housing one or more flat parts moving in translation and/or oscillating in said grooves, wherein the flat part comprises: a main flat body and a pair of springs protruding on opposed sides of the main flat body and resting against opposed surfaces of the respective groove; wherein each spring, when the flat part is inserted into the groove, pushes against the respective surface of the groove, so as to simplify/optimize oscillation of the flat part in said groove and/or to stabilize the flat part in said groove.

In one independent aspect, the invention relates to a drive chain for a needle of a knitting machine, optionally of a circular knitting machine, comprising at least one flat part according to the previous aspect or to one or more of the following aspects.

In one independent aspect, the invention relates to a drive chain for a needle of a circular knitting machine, wherein the drive chain, once mounted to the circular knitting machine, is inserted into a respective longitudinal groove of a needle-holding cylinder of said machine, wherein the drive chain, once mounted to the circular knitting machine, is located below a respective needle and is operatively placed between the respective needle and actuating cams of said machine.

In one aspect, said drive chain comprises: a sub-needle arranged below the needle and engaged to the needle so as to move axially in the respective longitudinal groove together with said needle.

In one aspect, the sub-needle comprises a moving butt that can be radially shifted between an operating position, in which it is extracted from the needle-holding cylinder so as to engage with respective first paths defined by first actuating cams and cause the activation of the needle, and a non-operating position, in which it is retracted in the needle-holding cylinder so as not to engage with said first paths.

In one aspect, said drive chain comprises: a selector partly located below the sub-needle and partly beside the sub-needle, wherein the selector is a flat part according to one or more of the aspects listed herein.

In one aspect, the selector is or can be radially coupled to the sub-needle.

In one aspect, the selector is configured for oscillating between an active position and a rest position, so as to control a shifting of the moving butt between the operating position and the non-operating position.

In one aspect, the selector is configured for oscillating between an active position, in which it pushes the moving butt in the operating position, and a rest position, in which it allows the moving butt to get back to the non-operating position.

In one aspect, the selector is axially decoupled from the sub-needle and from the needle so that the needle and the sub-needle are never pushed or pulled axially by said selector.

In one independent aspect, the invention relates to a knitting machine, optionally a circular knitting machine, comprising a plurality of drive chains according to one or more of the aspects listed herein.

In one independent aspect, the invention relates to a circular knitting machine comprising: a needle-holding cylinder having a plurality of longitudinal grooves arranged around a central axis of the needle-holding cylinder; a plurality of needles, each being housed in a respective longitudinal groove; actuating cams arranged around the needle-holding cylinder; wherein said needle-holding cylinder is movable with respect to the actuating cams around the central axis for causing or allowing the movement of the needles along the longitudinal grooves so as to enable stitch formation by said needles; a drive chain for each needle inserted into the respective longitudinal groove, located below the respective needle and operatively placed between the respective needle and said actuating cams; wherein said drive chain is in accordance with one or more of the aspects listed herein.

In one aspect, the machines comprises: at least one selecting device acting upon command upon the selectors for controlling the switching thereof between the active position and the rest position.

In one aspect, the selecting device causes the switching of the selectors to the active position.

The Applicant has verified that the invention allows to achieve the aims set above.

In particular, the Applicant has verified that the invention allows to ensure the correct positioning and movements of the flat part in the respective groove.

In particular, the Applicant has verified that the invention allows to:

-   -   brake/stabilize the flat part as required;     -   ensure an accurate oscillation of the flat part, in particular         of the selector mentioned above, around an axis of oscillation;     -   obtain at the same time the desired stabilization/braking and an         accurate oscillation of the flat part;     -   ensure the accurate positioning of the flat part inside the         groove, meaning the distance from the two opposed lateral         surfaces of the groove itself;     -   reduce frictions as much as possible and thus reduce wear and         maintenance.

Moreover, the Applicant has verified that the invention allows to simplify from a structural point of view the moving mechanisms of the needles and, if necessary, also the cams and therefore the machine as a whole. In particular, each drive chain or catenary is made of only two elements: the sub-needle and the selector.

The Applicant has also verified that the invention, though with a small number of elements, is highly flexible and allows to perform several knitting operations.

The Applicant has also verified that the oscillation of the selection, which is independent from the translation of the sub-needle and needles, allows to device where and when the butt of the sub-needle should be radially extracted/retracted, whatever the axial position of the selector and its axial travel range.

The Applicant has also verified that the axial position of the selector can also be kept fixed or basically fixed or anyhow the possible axial movement of the selector is independent from the axial travel range of the sub-needle and needle and is much smaller than the movement of the sub-needle and needle.

Further aspects of the invention are listed below.

In one aspect, opposed lateral portions of the springs, configured for contacting the surfaces of the groove, are located along an axis basically orthogonal to the main flat body.

In one aspect, said axis basically orthogonal to the main flat body is an axis of oscillation of the flat part in the groove.

In one aspect, the main flat body acts basically in a plane and the springs develop laterally with respect to said plane.

In one aspect, considering a longitudinal axis of the flat part, the springs are located basically in the same axial position as the flat part.

In one aspect, the opposed lateral portions of the springs exhibit respective contact areas with the surfaces of the groove, wherein optionally each of said contact areas is a point or a line or a surface.

In one aspect, when the springs are undeformed, i.e. the flat part is not in the groove, the springs protrude laterally beyond a thickness of the main flat body.

In one aspect, a distance between the opposed lateral portions of the springs when the latter are undeformed, i.e. the flat part is not in the groove, is between 0.05 and 2 mm.

In one aspect, a distance between the opposed lateral portions of the springs when the latter are deformed, i.e. the flat part is in the groove, is between 0.3 and 1.5 mm.

In one aspect, each of the springs comprises a bow-shaped plate with its convexity pointing outwards with respect to the main flat body, i.e. towards the respective surface of the groove.

In one aspect, the bow-shaped plate is elastically deformable.

In one aspect, the opposed lateral portions of the springs correspond to the tops of the bow-shaped plates.

In one aspect, the elastic deformation of the springs causes the opposed lateral portions to get mutually closer to one another.

In one aspect, the bow-shaped plate has a main direction of development that is basically parallel to a longitudinal axis of the flat part.

In one aspect, in its contact area the bow-shaped plate, when at rest, has a bending radius optionally between 2 mm and 25 mm.

In one aspect, the bow-shaped plate exhibits only one end joined to the main flat body.

In one aspect, the bow-shaped plate is connected to the main flat body protruding from it.

In one aspect, a distal end, opposed to the proximal end, of the bow-shaped plate is free.

In one aspect, the proximal end of the bow-shaped plate is located on the same plane as the respective distal end, optionally near a middle plane of the main flat body.

In one aspect, the two bow-shaped plates are located on opposed sides of a middle plane of the main flat body.

In one aspect, the bow-shaped plates cross each other.

In one aspect, a crossing area between the bow-shaped plates is near its proximal ends.

In one aspect, the bow-shaped plates have their proximal ends located on opposed sides of a middle plane of the main flat body and have the respective contact areas or portions, and optionally also the distal ends, arranged on inverted opposed sides of said middle plane.

In one aspect, the proximal ends and/or the distal ends of each bow-shaped plate are basically located in a middle plane of the main flat body.

In one aspect, the main flat body exhibits a through opening and the springs are located in said through opening.

In one aspect, the main flat body exhibits a pair of recesses located on opposed sides of the main flat body and the springs are located each in one of said recesses.

In one aspect, the main flat body exhibits a thin wall (thinner than a thickness of the main flat body) located in the through opening or delimiting said pair of recesses.

In one aspect, the proximal end of each bow-shaped plate is joined to the thin wall.

In one aspect, the distal ends of each bow-shaped plate rest against said thin wall and can freely slide with respect to said thin wall.

In one aspect, the proximal end is joined to at least one edge of the through opening.

In one aspect, the proximal ends and/or the distal ends of each bow-shaped plate are located between opposed edges of the through opening or of each recess.

In one aspect, the distal end faces at a distance an edge of the through opening or of the respective recess.

In one aspect, when the bow-shaped plate is deformed, the distal end can freely move in the opening or in the respective recess.

In one aspect, the bow-shaped plate exhibits a rectangular plan shape.

In one aspect, the through opening or each of the recesses exhibits a rectangular shape.

In one aspect, the through opening or each of the recesses exhibits first edges opposed to one another, and second edges opposed to one another, wherein the proximal end and the distal end of the bow-shaped plate are located between the first opposed edges and the distal end faces at a distance one of the second edges.

In one aspect, the thin wall comprises two portion, each being located in the through opening and joined to one of the second edges of said through opening.

In one aspect, the two portions of the thin wall are at a distance from one another.

In one aspect, a width of the bow-shaped plate is basically the same as (slightly small than) a distance between the two first edges.

In one aspect, optionally when the bow-shaped plates cross each other, each of the bow-shaped plates exhibits a width basically corresponding to half the distance between the two first edges.

In one aspect, optionally when the bow-shaped plates cross each other, each of the bow-shaped plates, at least in the contact portion, occupies a width corresponding to a respective half of the through opening.

In one aspect, the distal ends of the bow-shaped plates whose width basically corresponds to half the distance between the two first edges, converge towards a central axis of the through opening and mutually overlap.

In one aspect, the springs are symmetrical or basically symmetrical with respect to a middle plane of the main flat body.

In one aspect, opposed lateral portions of the springs, configured for contacting the surfaces of the groove, are symmetrical or basically symmetrical with respect to a middle plane of the main flat body.

In one aspect, the springs are configured for keeping the flat part on a median plane of the respective groove.

In one aspect, only the springs are configured for touching the opposed surfaces of the respective groove, while the main flat body lies at a distance from said surfaces.

In one aspect, the flat part is chosen from the group comprising: a needle, a jack, a sub-needle, a selector, a pushing unit.

In one aspect, the drive chain only comprises said sub-needle and said selector or consists of said sub-needle and said selector.

In one aspect, the circular knitting machine is a socks machine, i.e. a machine configured for manufacturing fabrics with floated/trimmed and/or jacquard motifs.

In one aspect, the drive chain is configured for decoupling an axial movement of the needle and/or of the sub-needle from an axial movement of the selector.

In one aspect, the actuating cams comprise said first actuating cams defining respective first paths for the moving butt. The first actuating cams extend all around the needle-holding cylinder.

In one aspect, the sub-needle comprises a first portion that is axially movable in the respective groove, and a second portion carrying the respective butt, wherein the second portion is also radially movable, wherein optionally the second portion is hinged to the first portion.

In one aspect, the selector can be operatively engaged with the second portion.

In one aspect, the sub-needle comprises a spring operatively placed between the first portion and the second portion so as to elastically push the second portion and the moving butt towards the non-operating position.

In one aspect, the selector pushes and keeps the moving butt to the operating position acting against the spring.

In one aspect, the sub-needle is axially movable together with the needle between a completely lowered position and a completely raised position, wherein the selector is partly placed beside the sub-needle so as to act upon the moving butt both when the sub-needle is in the completely lowered position and when the sub-needle is in the completely raised position.

In one aspect, the sub-needle comprises an auxiliary butt which develops radially from the first portion and is stiffly connected to the first portion.

In one aspect, the actuating cams comprise second actuating cams defining respective second paths for the auxiliary butt. The second actuating cams extend all around the needle-holding cylinder.

In one aspect, the selector exhibits a first part configured for radially pushing and keeping the moving butt in the operating position, and a second part opposed to the part, which can be engaged with said at least one selecting device.

In one aspect, on said at least one selecting device, the selector is oscillated between an active position, in which it pushes the moving butt in the operating position, and a rest position, in which it allows the moving butt to get back to the non-operating position.

In one aspect, the selector exhibits an elongated shape.

In one aspect, the selector is configured for oscillating around a middle point placed between the first part and the second part.

In one aspect, the selector is configured for oscillating around said axis basically orthogonal to the main flat body, wherein said axis basically orthogonal to the main flat body is orthogonal to the central axis and gets across said middle point.

In one aspect, a guide is arranged all around the needle-holding cylinder, wherein said needle-holding cylinder is movable with respect to the guide around the central axis.

In one aspect, the guide is integral with the actuating cams, i.e. it does not turn around the central axis with respect to the actuating cams.

In one aspect, a butt of the selector is placed at a lower end of said selector and is engaged with the guide.

In one aspect, the guide is configured for locking or unlocking the oscillation of the selector as a function of the position of the selector around the central axis of rotation.

In one aspect, the selector oscillates by effect of the selecting device and/or of the spring.

In one aspect, the selector comprises at least one tooth radially pointing outwards, away from the central axis, which can be engaged by the selecting device.

In one aspect, said at least one tooth is located on the second part, optionally between the middle point and the butt of the selector.

In one aspect, the selector comprises an end stop acting against a retainer configured for limiting an axial travel of the selector.

In one aspect, the selecting device is an actuator, optionally of magnetic or piezoelectric type.

In one aspect, the actuator comprises a plurality of levers, wherein each lever is movable under control between a first position and a second position.

In one aspect, the levers are configured for working, i.e. for engaging, with the teeth of the selectors.

In one aspect, the engagement of a lever with a tooth of the selector causes the selector to switch to the active position.

In one aspect, a plurality of selecting devices are arranged around the needle-holding cylinder and are stationary with respect to the actuating cams.

In one aspect, the oscillating movement of the selector is controlled by a plurality of selecting devices arranged around the needle-holding cylinder.

In one aspect, on said at least one selecting device, the guide allows the selector to oscillate between the active position and the rest position and, in other places, the guide prevents the selector from oscillating between the active position and the rest position.

In one aspect, on said at least one selecting device, the selector is pushed towards the active position by said at least one selecting device, or wherein the selector is pushed towards the rest position by the moving butt, which is in its turn elastically pushed towards the respective non-operating position.

Further characteristics and advantages shall be more evident from the detailed description of a preferred embodiment of a circular knitting machine, of a drive chain and a flat part according to the present invention.

DESCRIPTION OF THE DRAWINGS

This description shall be made below with reference to the accompanying drawings, provided to a merely indicative and therefore non-limiting purpose, in which:

FIG. 1 shows a portion of a needle-holding cylinder of a circular knitting machine according to the present invention, in which a drive chain of a needle can be seen, coupled with actuating cams developed in a plane;

FIGS. 2A and 2B show respective magnified portions of the drive chain of FIG. 1;

FIGS. 3A and 3B show two possible positions of the drive chain of the preceding figures;

FIGS. 4A, 4B, 4C and 4D show respective magnified portions in different operation positions of a lower area of the drive chain of the preceding FIGS. 3A and 3B;

FIG. 5 shows a sectioned view of a part of an element of the drive chain as in the previous figures;

FIGS. 6 and 7 show respective elements of the machine of FIG. 1;

FIG. 8 is a magnified view of a portion of an element of the drive chain as in the previous figures;

FIG. 9 shows a view of the portion of FIG. 8;

FIG. 10 shows a sectioned view of the portion of FIGS. 8 and 9 in a first configuration;

FIG. 11 shows the portion of FIG. 10 in a second configuration;

FIG. 12 shows a different view of the portion as in FIGS. 8, 9, 10 and 11;

FIG. 13 shows a sectioned view of the variant of the portion of FIG. 10;

FIG. 14 shows the variant of FIG. 13 according to a different view;

FIG. 15 shows a sectioned view of a further variant of the portion of FIG. 10;

FIG. 16 shows the further variant of FIG. 15 according to a different view.

DETAILED DESCRIPTION

With reference to the figures mentioned, the numeral 1 globally designates a knitting head of a circular knitting machine. For instance, the circular knitting machine shown is a machine configured for manufacturing fabrics with floated/trimmed and/or jacquard motifs.

The circular knitting machine comprises a basement, not shown since it is of known type, constituting the supporting structure of the machine, and said knitting head 1 mounted onto the basement.

The knitting head 1 is equipped with a needle-holding cylinder 2, with a plurality of needles 3 mounted onto the needle-holding cylinder 2, and with control devices apt to selectively actuate the needles 3 so as to enable the production of a fabric.

The needle-holding cylinder 2 is usually mounted in vertical position onto the basement, with the needles 3 arranged vertically and protruding beyond an upper edge of the needle-holding cylinder 2. For instance, the needle-holding cylinder 2 has a reference diameter of about 100 mm and a height of about 350 mm.

The needle-holding cylinder 2 has a plurality of longitudinal grooves 4 obtained on a radially outer surface of the cylinder 2. The longitudinal grooves 4 are arranged around a central axis “X-X” (vertical) of the needle-holding cylinder 2 and develop parallel to said central axis “X-X”. Each longitudinal groove 4 houses a respective needle 3 and a respective drive chain 5 or “catenary” comprising a plurality of flat parts.

FIG. 1 shows for the sake of simplicity only one drive chain 5 and only one needle 3 that is or can be operatively associated to a knockover sinker “P” radially moving in respective grooves obtained in a crown of the machine, which is known per se and not described in further detail.

Actuating cams “C” are arranged as a casing around the needle-holding cylinder 2 and lie facing the radially outer surface of the needle-holding cylinder 2 and thus the longitudinal grooves 4 and the drive chains 5. These actuating cams “C” are defined e.g. by plates and/or grooves arranged or obtained on a radially inner surface of the casing.

For the sake of clarity, in FIG. 1 the casing and the actuating cams “C” have been represented developed in a plane and beside the drive chain 5 coupled with one of the needles 3.

In the embodiment shown, the casing of the actuating cams “C” is basically stationary, whereas the needle-holding cylinder 2 rotates (with a continuous or alternating motion in both directions) around the central axis “X-X” so as to generate a relative rotational motion between the drive chains 5 (with the needles 3) and the actuating cams “C”. To this purpose, a motor is operatively connected to the needle-holding cylinder 2 and is controlled by a control unit configured for controlling the operation of the machine and its movements. In particular, the motor controls the rotation of the needle-holding cylinder 2 in a first direction of rotation or in a second direction of rotation opposed to the first one.

As shall be described below in further detail, the drive chains 5 can be operatively coupled with the actuating cams “C” so as to turn said relative rotational motion between the needle-holding cylinder 2 and the actuating cams “C” into axial movements of the needles 3 along the longitudinal grooves 4, so as to enable stitch formation by said needles 3 cooperating with the knockover sinkers “P”. The actuating cams “C” define paths extending around the needle-holding cylinder 2, which are/can be engaged by butts belonging to the drive chains 5.

Therefore, each drive chain 5 is operatively placed between the respective needle 3 and the actuating cams “C”.

Suitable devices, not shown, feed the yarns to be knitted on one or more yarn feeding points (known as feeds) usually arranged above the needle-holding cylinder 2. The circular machine shown in the accompanying figures exhibits only yarn feed.

Reference shall now be made to a single drive chain 5 coupled with a respective needle 3, as shown in FIGS. 1, 2A, 2B, 3A and 3B. The relative positions of the various elements are described with reference to the drive chain 5 with the respective needle 3 correctly installed in the respective groove 4 of the needle-holding cylinder 2 in vertical position. The needle 3 is arranged on an upper edge of the needle-holding cylinder 2 and the drive chain 5 develops below the needle 3 as far as near a base of the needle-holding cylinder 2.

As can be better seen in FIGS. 1, 2A, 2B, 3A and 3B, the drive chain 5 comprises two flat parts and in particular: a sub-needle 6 arranged directly below the needle 3, and a selector 7 located partly below the sub-needle 6 and partly beside the sub-needle 6. In other words, looking at FIG. 1, a portion of the selector 7 is located laterally with respect to the sub-needle 6 and is positioned between the central axis “X-X” and the sub-needle 6 itself. Since the drive chain 5 is housed in the respective groove 4, said portion is located behind the sub-needle 6, i.e. radially further inner in the groove 4 with respect to the sub-needle 6.

The sub-needle 6 is arranged below the needle 3 and engaged to the needle 3 so as to move axially in the respective longitudinal groove 4 together with said needle 3. The sub-needle 6 and the selector 7 are metal parts. In a possible embodiment, not shown, the sub-needle 6 and the needle 3 can be integrated as one piece.

In the embodiment shown, the needle 3 has a foot 8 shaped as a kind of hook. When the needle 3 is correctly positioned in the longitudinal groove 4, the foot 8 is oriented radially outwards.

The sub-needle 6 exhibits a first portion 9. An upper end of the first portion 9 has a seat 10. The needle 3 is firmly connected to the sub-needle 6 by the insertion of the foot 8 into the seat 10. The connection between the foot 8 and the seat 10 is two-side, i.e. the needle 3 and the sub-needle 6 move axially integrally along the longitudinal groove 4. The connection between the foot 8 and the seat 10 constitutes a kind of hinge since the needle 3 and the sub-needle 6 are mutually integral in their vertical axial movement, but can slightly oscillate one with respect to the other on the mutual connection. This hinge moves along a longitudinal groove 4 base on the axial movement of the needle 3 and the sub-needle 6 which are mutually integral. The foot 8 can be easily connected to or disconnected from the seat 10 so as to make it easier to assemble or disassemble both elements.

An elastic extension 11 extends and projects from the main body 9 and faces axially downwards, i.e. towards the activating element 7. The elastic extension 11 is a sort of arm that can be bent elastically, i.e. works under bending like a spring.

The sub-needle 6 further a second portion 12 hinged to the first portion 9 and also developing from the first portion 9 downwards, i.e. towards the selector 7. A hinging pivot or center of rotation 13 of the second portion 12 on the first portion 9 is placed near a proximal end of the elastic extension 11, and the elastic extension 11 develops at least partly beside the second portion 12. The elastic extension 11 is slightly curved and exhibits a terminal or distal end resting and operatively active against the second portion 12. The terminal end of the elastic extension 11 is at a distance from the center of rotation 13 of the second portion 12.

In further detail, in the embodiment shown, the second portion 12 comprises a rod and a supporting portion which develops beside the rod and carries a moving butt 14. The supporting portion exhibits its own rectilinear lateral edge from the moving butt 14 extends laterally. The rod exhibits a proximal end hinged to the first portion 9 in said center of rotation 13, and a terminal end, opposed to the proximal end, which extends axially beyond the supporting portion and beyond the moving butt 14.

The supporting portion and thus also the moving butt 14 are at a distance from the center of rotation 13 of the second portion 12. The supporting portion and the moving butt 14 lies below the terminal end of the elastic extension 11 and this terminal end rests against the rod.

The sub-needle 6 further comprises an protrusion 15 that is integral with the first portion 9 and stiffly connected to the first portion 9. The protrusion 15 exhibits an elongated shape and extends basically parallel to the elastic extension 11 and on a side of said elastic extension 11 opposed to the second portion 12. In other words, the elastic extension 11 is placed between the second portion 12 and the protrusion 15. The supporting portion of the second portion 12 is located below a distal end of the protrusion 15.

The sub-needle 6 also comprises an auxiliary butt 16 that develops radially from the first portion 9 and is stiffly connected to the first portion 9. The auxiliary butt 16 is located near the center of rotation 13 and is therefore arranged higher than the moving butt 14 (when the drive chain 5 is correctly installed on the needle-holding cylinder 2).

The first portion 9 of the sub-needle 6 is only movable with an axially translational motion along the respective longitudinal groove 4 together with the respective needle 3. The auxiliary butt 16 of the sub-needle 6 is thus axially movable together with the first portion 9 and radially stationary.

The second portion 12, beyond being axially movable with the first portion 9, can oscillated around the center of rotation 13 and with respect to the first portion 9. The rotation or oscillation of the second portion 12 allows to radially shift the moving butt 14 between an operating position (FIG. 3B), in which it is extracted from the needle-holding cylinder 2, and a non-operating position (FIG. 3A), in which it is retracted in the needle-holding cylinder 2.

The spring defined by the elastic extension 11 contrasts the rotation of the second portion 12 to the operating position (FIG. 3B) of the moving butt 14 or, in other words, tends to push the second portion 12 and the moving butt 14 to the non-operating position of FIG. 3A. In the non-operating position of said moving butt 14, the elastic force exerted by the elastic extension 11 keeps the moving butt 14 inside the respective groove.

The protrusion 15 acts as an end stop for the deformation of the elastic extension 11 and for the oscillation of the first portion 12. Moreover, an upper surface of the supporting portion slides and/or rests against a distal end of the protrusion 15, at least when the moving butt 14 is the operating position or is near the operating position.

This ensures a given stiffness for the sub-needles 6. Moreover, as can be seen in FIG. 3B, the protrusion 15 defines, together with the rest of the first portion 9, a continuous edge pointing radially outwards and towards the actuating cams “C”. When the moving butt 14 is the operating position of FIG. 3B, the lateral edge of the supporting portion is aligned with the continuous edge of the first portion 9.

The needle 3 is provided with a braking system, known per se and therefore not described in detail, whose function is to keep said flat parts (needle 3 and sub-needle 6) in their position inside the respective groove 4. The axial position of the assembly made up of the needle 3 and sub-needle 6 along the groove 4 is kept thanks to the braking system as long as the sub-needle 6 is stressed by the actuating cams “C”. In other words, when the needle 3 and the sub-needle 6 are raised or lowered, inside their own sliding groove 4, as a result of the interaction with the actuating cams “C”, said needle 3 and sub-needle 6 then keep their axial position thanks to the braking system on the needle 3.

The selector 7 exhibits an elongated shape in the direction of the groove 4 and comprises a main flat body 199 lying in a respective plane. The main flat body 100 exhibits a first part 17 or upper part and a second part 18 or lower part and is configured for oscillating around a middle point 19 located between the first part 17 and the second part 18 and around a respective axis “Y-Y” (FIG. 2B) orthogonal to the main flat body 100, orthogonal to the central axis “X-X” and getting across said middle point 19. The selector 7 is further configured for making a limited axial travel in the respective groove 4. The selector 7 is therefore a flat part configured for oscillating and translating in the respective groove 4.

To this purpose, the selector 7 comprises a pair of springs 20 arranged on opposed sides of the main flat body 100 and developing laterally with respect to the plane of the main flat body 100. The springs 20 are configured for resting against opposed lateral surface 4 a of the respective groove 4 (FIG. 11), so as to make it easier for the selector 7 to oscillate in said groove 4. Each spring 20, when the selector 7 is inserted into the groove 4, pushes against the respective surface of the groove 4, so as to make it easier for the selector 7 to oscillate in said groove 4 and/or to stabilize the selector 7 in said groove 4.

As can be better seen in FIGS. 5, 8, 9, 10, 11 and 12, each of the springs 20 comprises a bow-shaped plate whose convexity points towards the respective surface 4 a of the groove 4. The bow-shaped plate exhibits only one proximal end 21 joined, e.g. welded, to the main flat body 100, whereas the opposed distal end 22 can freely move by effect of the deformation of the bow-shaped plate due to the interaction with the lateral surface 4 a of the groove 4. The two bow-shaped plates protrude laterally and are located partly in a through opening 23 obtained in the main flat body 100. The two bow-shaped plates ensure a small contact surface of the selector 7 with the opposed lateral surfaces 4 a of the respective groove 4, so as to reduce frictions during oscillation, and reduce at the same time possible unwanted vibrations of the selector 7. In the embodiment shown, the springs 20 are symmetrical or basically symmetrical with respect to a middle plane “P” of the main flat body 100, so as to keep the selector 7 centered in the groove 4, i.e. in a median plane of the groove 4. The main flat body 100 of the selector 7 therefore does not touch the lateral surfaces 4 a of the groove 4. Median plane “P” of the main flat body 100 means the plane parallel and at the same distance from opposed faces of the main flat body 100 (FIG. 9).

In further detail, in the non-limiting embodiment shown, the through opening 23 exhibits (FIGS. 10, 11 and 12) a rectangular shape with its two first longer edges oriented parallel to a longitudinal axis “K-K” of the selector 7 and its two shorter edges (shorter than the first edges) orthogonal to the first longer edges.

Each bow-shaped plate exhibits a rectangular plan shape so that it can be housed between the two first edges and the two second edges. A width of the bow-shaped plate is basically the same as (slightly small than) a distance between the two first edges (FIG. 12). A length of the bow-shaped plate, at least when it is in its rest configuration, is shorter than a distance between the two second edges (FIG. 12). Said proximal end 21 of the bow-shaped plate is joined to one of the second edges, and the distal end 22, at least when the bow-shaped plate is in its rest configuration, is kept at a distance from the other of the second edges.

As shown in FIGS. 10 and 11, the two proximal ends 21 of the two bow-shaped plates are near one another on the middle plane “P” of the main flat body 100, i.e. on the second edge to which they are joined. Also the distal ends 22 of the two bow-shaped plates are near one another on the middle plane “P” of the main flat body 100 and can freely move one with respect to the other. The two bow-shaped plates 20 are thus located on opposed sides of the middle plane “P” of the main flat body 100.

The proximal ends 21 placed near one another exhibit a global thickness corresponding to or smaller than a thickness of the main flat body 100. Also the distal ends 22 placed near one another exhibit a global thickness corresponding to or smaller than the thickness of the main flat body 100.

Each bow-shaped plate exhibits a convexity pointing outwards with respect to the main flat body 100, i.e. towards the respective surface 4 a of the groove 4, and is elastically deformable. Therefore, the two bow-shaped plates are near one another on their proximal 21 and distal ends 22 and are at a distance on their intermediate portions corresponding to the tops of the respective curves. These intermediate portions define opposed lateral portions of the springs 20 which exhibit respective contact areas 101 with the surfaces 4 a of the groove 4. In the embodiment shown, each of said contact areas 101 is a line or a surface. The axis “Y-Y” gets across said contact areas 101 and is orthogonal to the main flat body 100. In its contact area 101 each bow-shaped plate, when it is in rest position (FIGS. 9 and 10), exhibits a radius of curvature e.g. of 3 mm.

In the rest or undeformed configuration of FIG. 10, the intermediate portion of the bow-shaped plates protrude laterally from the opening 23 and from the main flat body 100. A distance between the opposed lateral portions of the springs 20 when the springs 20 are undeformed, since the selector 7 is not in the groove 4, is e.g. 1.5 mm.

In the deformed configuration of FIG. 11, in which the selector is in the groove 4, the intermediate portions of the bow-shaped plates are closer to one another and they may be put near one another. A distance between the opposed lateral portions of the springs when the springs 20 are undeformed, i.e. the selector 7 is not in the groove, corresponds to the width of the groove 4, e.g. 0.8 mm.

The elastic deformation of the springs 20 involves a mutual approach of the opposed lateral portions, i.e. Of the intermediate portions of the bow-shaped plates. Moreover, the bow-shaped plate reduce their curvature and the distal ends 22 get near the second edge which they are facing.

FIGS. 13 and 14 show a variant of the springs 20. In this variant, the proximal ends are inserted into a housing obtained in the main body 100. The portions of the bow-shaped plates 20 protruding into the opening 23 exhibit a width corresponding to about half the width of the opening 23. As can be seen in FIG. 14, these protruding portions are near one another in the length extending from the proximal ends 21 as far as short before the distal ends 22. Moreover, the bow-shaped plates 20 cross each other, i.e. the proximal ends 21 are located on opposed sides of the middle plane “P” of the main flat body 100 and, further to the right in FIGS. 13 and 14, the bow-shaped plate 20 lying on one of these sides crosses, near the proximal ends 21, the middle plane “P” and vice versa the other bow-shaped plate 20. Therefore, the bow-shaped plates 20 exhibit the respective contact areas or portions 101 and also the distal ends 22 arranged on opposed sides inverted with respect to the proximal ends 21. The distal ends 22 and the bow-shaped plates 20 thus converge towards a central axis of the through opening 23 and mutually overlap. In FIG. 14 it can be seen that each distal end 22 is curved towards the middle point of the through opening 23 and lies over the other distal end 22. The solution just described allows to connect in a safer and more resistant manner the springs 20 to the main flat body 100 and to reduce the overall size as well.

FIGS. 15 and 16 show a further variant of the springs 20, wherein the bow-shaped plates do not cross each other and each exhibits a width basically corresponding to the width of the through opening 23, like in FIGS. 10, 11 and 12. In this variant, however, two portions of a thin wall 102 (thinner than a thickness of the main flat body 100) are located in the through opening 23 and develop from the second (shorter) edges of the through opening 23, respectively, and are located basically on the middle plane “P” of the main flat body 100. The two portions of the thin wall 102 are at a distance from each other, so that the opening 23 is still a through opening.

The distal end 21 of each bow-shaped plate 20 is joined, e.g. welded, to one of the portions of the thin wall 102. The distal ends 22 of each bow-shaped plate 20 rest against the other portion of the thin wall 102 and can freely slide with respect to said thin wall 102.

This embodiment allows to make it easier, thanks to the thin wall 102, for the springs 20 and the main flat body 100 to be connected to one another.

In a further variant, not shown, there is only one thin wall 102, i.e. the two portions are joined to each other and therefore the opening 23 is not a through opening, but the main flat body 100 exhibits, instead of the opening 23, a pair of recesses located on their opposed sides and the springs 20 are located each in one of said recesses.

The first part 17 of the selector 7 extends partly beside the second portion 12 of the sub-needle 6 and in a radially further inner position than said second portion 12, i.e. moved further towards the central axis “X-X”. This first part 17 is configured for engaging and pushing against the second portion 12. In particular, the selector 7 is configured for oscillating, by rotating around the middle point 19, between an active position in which its first part 17 pushed the second portion 12 and the moving butt 14 towards the operating position (FIG. 3B), and a rest position in which it allows the second portion 12 and the moving butt 14 to get back to the non-operating position (FIG. 3A). In FIG. 3B, the first part 17 of the selector 7 is shifted radially outwards and pushed and keeps the moving butt 14 in the operating position by acting against the elastic force exerted by the elastic extension 11. In FIG. 3A, the first part 17 of the selector 7 is shifted radially inwards and the elastic force of the elastic extension 11 pushed and keeps the second portion 12 in the non-operating position.

The selector 7 exhibits a butt 24 placed at a lower end of its second part 18 and extending radially outwards, like the moving butt 14 and the auxiliary butt 16. The butt 24 of the selector 7 exhibits a wedge-like shape, i.e. diverging radially outwards.

The selector 7 further comprises at least one tooth 25 placed on the second part 18 between the middle point 19 and the butt 24 of the selector 7 and pointing also radially outwards.

Furthermore, the selector 7 is provided with a bow-shaped, convex surface 26 arranged on its edge pointing radially outwards and acting against an abutment element 27 (which is stationary with respect to the casing with the actuating cams “C) and its function is to better guide the oscillation of said selector 7. On said bow-shaped convex surface 26, also an edge 26 a pointing radially inwards is bow-shaped and convex and rests against a bottom of the respective groove 4. Also the function of this bow-shaped, convex edge 26 a is to guide the oscillation of the selector 7.

The selector 7 further comprises an end stop 28 acting against a retainer 29, which is also stationary with respect to the casing, for limiting the axial travel of the selector 7, as shall be described further below.

The casing is provided with a guide 30 extending all around the needle-holding cylinder 2, wherein the needle-holding cylinder 2 is movable with respect to the guide 30. In the embodiment shown, the guide 30 is stationary, like the actuating cams “C”, whereas the needle-holding cylinder 2 rotates. The butt 24 of the selector 7 is engaged with the guide 30. The guide 30 is shaped so as to lock or unlock the oscillation of the selector 7 depending on the angular position of the selector 7 around the axis of rotation “X-X”.

The guide 30 comprises a track defined by a circular track/groove 31, which opens towards the needle-holding cylinder 2, extends all around the latter and is configured for receiving the butt 24 of the selector 7. As can be seen in FIG. 1, the circular track/groove 31 exhibits first circumferential lengths 32 located at a higher level, and second circumferential lengths 33 located at a lower level. The first circumferential lengths 32 alternate with the second circumferential lengths 33 along a circumferential development of the track (developing in a plane in FIG. 1). Connecting portions, i.e. ascending or descending ramps, connect the first circumferential lengths 32 to the second circumferential lengths 33. Moreover, the first circumferential lengths 32 exhibit a first width, measured along an axial/vertical direction, which is larger than a second width of the second circumferential lengths 33. Moreover, the first circumferential lengths 32 exhibit an axial width that is larger than a maximum axial size (measured along a direction parallel to the central axis “X-X”) of the butt 24 of the selector 7.

A section of the track on one of the first circumferential lengths is shown in FIG. 4C. A section of the track on one of the second circumferential lengths is shown in FIGS. 4A and 4D. FIG. 4B shows the track in a sectioned view on one of the connecting portions.

At least on the second circumferential lengths 33 (FIG. 4A), the track exhibits a sectioned view with a different geometry. In other words the track widens radially outwards, i.e. getting away from the central axis “X-X” and is basically countershaped to the butt 24 of the selector 7.

The guide 30 further comprises an abutment ring 34 basically placed in front of the track and in a radially inner position at a distance from said track. The abutment ring 34 has an upper surface 35 placed at a constant level. The upper surface 35 of the abutment ring 34 is located basically at the same level as a lower edge of the first circumferential lengths 32 of the track (FIG. 4C) and at a higher level than a lower edge of the second circumferential lengths 33 of the track (FIGS. 4A, 4B, 4D).

The selector 7 rest upon different elements of the guide 30 depending on its position around the central axis “X-X”.

The machine comprises a plurality of selecting devices 36, 37 arranged in a stationary manner around the needle-holding cylinder 2 and facing the second portion 18 of the selectors 7. The selecting devices 36, 37 are magnetic or piezoelectric lever actuators located on the first circumferential lengths 33 of the track (FIG. 1).

Each selecting device 36, 37 is configured for acting under control upon the selectors 7 so as to cause them to switch to the respective active position.

In the embodiment shown in FIGS. 6 and 7, the actuator 36, 37 comprises an array of levers 38 projecting from a front face of the actuator 36, 37 and facing, when the actuator 36, 37 is mounted to the machine 1 in operating position, the needle-holding cylinder 2 and the teeth 25 of the selectors 7. The array of levers 38 comprises a plurality of levers 38 overlapping and aligned along a respective common vertical axis. Each lever 38 has an asymmetrical shape with respect to a plane of symmetry in which said common vertical axis lies.

Each of the levers 38 is oscillating, e.g. by means of a piezoelectric control managed by a control unit of the machine, around a respective horizontal axis orthogonal to the common axis, between a first raised position (hatched line) and a second lowered position (continuous line). By means of said oscillation, the lever 38 is raised and/or lowered and interacts with a respective tooth 25 of the selector 7. In the embodiment shown, each lever 38 engages with a tooth 25 of a selector 7 when in the first raised position, ad does not engage with, i.e. avoids, the tooth 25 of the selector 7 when in the second lowered position.

The engagement of a lever 38 with a tooth 25 of the selector 7 causes the selector 7 to switch to the active position. Therefore, in each selecting device 36, 37, the selector can be pushed towards the active position by the selecting device 36, 37 or the selector 7 can be pushed towards the rest position by the second portion 12 of the sub-needle 6, which is in turn pushed elastically towards the respective non-operating position.

The machine is equipped with a first series of selecting devices 36 working when the needle-holding cylinder 2 rotates with respect to the actuating cams “C” in the first direction of rotation, and with a second series of selecting devices 37 working when the needle-holding cylinder 2 rotates with respect to the actuating cams “C” in the second direction of rotation, opposed to the first one.

As can be seen in FIG. 1, the circular track/groove 31 exhibits first circumferential lengths 32 with a larger circumferential extension (two in the embodiment shown) and first circumferential lengths 32 with a smaller circumferential extension (seven in the embodiment shown). A single selecting device of the first series 36 is coupled with six of the first circumferential lengths 32 with a smaller circumferential extension. A single selecting device of the second series 37 is coupled with one of the first circumferential lengths 32 with a smaller circumferential extension. A pair made up of a selecting device of the first series 36 and of a selecting device of the second series 37 is coupled with each of the two first circumferential lengths 32 with a larger circumferential extension.

The actuating cams “C” comprise first actuating cams 39 defining respective first paths for the moving butt 14, and second actuating cams 40 defining respective second paths for the auxiliary butt 16. The first actuating cams 39 and the second actuating cams 40 extend all around the needle-holding cylinder 2. The first actuating cams 39 are arranged at a lower level than the second actuating cams 40. In other words, the first actuating cams 39 define a first sector extending around the needle-holding cylinder 2 and operatively associated to the moving butt 14. The second actuating cams 40 define a second sector extending around the needle-holding cylinder 2, lying at a higher level than the first sector and operatively associated to the auxiliary butt 16.

The first actuating cams 39 delimit/define a plurality of first paths for the moving butt 14. In particular, along a circumferential development of the first actuating cams 39, these first actuating cams 39 define one or more first paths depending on the angular position around the central axis “X-X”. For instance, the first actuating cams 39 define a single first path in an area of the casing and three first paths placed one above the other in a different area of the casing. Also the second actuating cams 40 delimit/define a plurality of second paths for the auxiliary butt 16. For instance, the second actuating cams 40 define a second first path in an area of the casing and a plurality of second paths placed one above the other in a different area of the casing.

When the moving butt 14 is in its non-operating position, it does not engage with the first actuating cams 39 and does not follow any of the first paths. The auxiliary butt 16 is always in an operating position, i.e. apt to be caught by the second actuating cams 40. Some of said second actuating cams 40 are movable (hatched line in FIG. 1) between a catching position of the auxiliary butt 16 and a rest position. Others of said second actuating cams 40, conversely, are stationary. Due to the arrangement of the second actuating cams 40 and to the possibility to switch the movable ones to the rest position, there are some lengths in which the auxiliary butt 16 is not caught by the second actuating cams.

If the moving butt 14 is in its non-operating position (and thus does not engage with the first actuating cams 39) and in those lengths in which the auxiliary butt 16 is not caught by the second actuating cams 40, the needle 3 and the sub-needle 6 rotate around the central axis “X-X” keeping at a constant level thanks to the braking system on the needle 3. If the moving butt 14 is in its non-operating position (and thus does not engage with the first actuating cams 39) and in those lengths in which the auxiliary butt 16 is caught by the second actuating cams 40, the needle 3 and the sub-needle 6 are shifted axially by said second cams 40 while they rotate around the central axis “X-X”. When the moving butt 14 is in its operating position (and thus engages with the first actuating cams 39), it follows one of the first paths and the needle 3 and the sub-needle 6 are shifted axially by said first actuating cams 39 while they rotate around the central axis “X-X”. The moving butt 14 thus causes the activation of the needle 3 when it engages with one of the first paths.

Each selecting device 36, 37 and each first circumferential length 32 are therefore operatively associated with at least one or more of said first paths for causing the moving butt 14 to engage into said first path or into one of said first paths.

On the selecting devices 36, 37, i.e. on the first circumferential lengths 32, the guide 30 allows the selector 7 to oscillate between the active position and the rest position and, in other places, i.e. on the second circumferential lengths, the guide prevents the selector 7 from oscillating between the active position and the rest position. Moreover, in the selecting devices, the selector 7 is pushed towards the active position by said selecting devices 36, 37 or the selector 7 is pushed towards the rest position by the second portion 12 with the moving butt 14, which is in turn pushed elastically towards the respective non-operating position by the elastic extension 11. The selector 7 is axially decoupled from the sub-needle 6 and from the needle 3 so that the needle 3 and the sub-needle 6 are never pushed or pulled axially by said selector 7. The function of the selector 7 is therefore to activate or deactivate the moving butt 14 but not to push or pull axially the sub-needle 6. As a matter of fact, the drive chain is configured for decoupling an axial movement of the needle 3 and of the sub-needle 6 from the limited axial movement of the selector 7. The sub-needle 6 is axially movable together with the respective needle 3 between a completely lowered position (non-operating, low) and a completely raised position (non-operating, high), and the selector 7 is partly placed beside the sub-needle 6 so as to act upon the moving butt 14 both when the sub-needle 6 is in the completely lowered position and when the sub-needle 6 is in the completely raised position. For instance, a maximum axial travel range of the sub-needle 6 and of the needle 3 is of 30 mm, whereas the selector 7 shifts axially of 3 mm. The axial extension of the first part 17 or upper part of the selector 7 is such as to be able to always act against the second portion 12 of the sub-needle 6 whatever the axial position of the latter.

The first paths are configured for raising or lowering the moving butt 14 and therefore the needle 3 and sub-needle 6, making them move on the required axial travel, or for causing the auxiliary butt 16 to engage with the second paths. Thus, the combined action of the first and second paths raises or lowers the needle 3 and the sub-needle 6.

In the non-limiting example of embodiment shown, the moving butt 14 is pushed to the operating position by the selector 7 and goes back to the non-operating position by effect of the elastic extension 11. In other embodiments, not shown, this assembly can work in reversed order, i.e. the moving butt 14 is pushed to the operating position by the elastic extension 11 and goes back to the non-operating position by effect of a thrust exerted by the selector 7. Moreover, in embodiments not shown, the selecting device 36, 37 actively causes the selector 7 to switch to the rest position (instead of the active position).

The selection 7 described herein is therefore a flat part according to the invention. In other embodiments, not described herein, the flat part provided with the springs 20 can for instance differ from the selector 7 and be associated with a drive chain and/or with a machine differing from those described herein. For instance, the flat part according to the invention can be a needle, a sub-needle, a pushing unit, and so on.

The invention achieves important advantages.

First of all, the invention allows to overcome the drawbacks of prior art.

In particular, the invention allows to:

-   -   improve the accuracy with which the flat part is moved         (translation, oscillation or rototranslation) and/or position         longitudinally and/or transversally in the respective groove in         the various processing steps of the machine;     -   manage/adjust the friction/braking force developing between the         flat part and the groove housing it;     -   produce a machine which is globally simpler and more rational         from a structural point of view, cheaper to be produced and         maintained and also more reliable;     -   disconnect the axial movement of the needles from the movement         of the respective selectors, the selectors working basically         only by oscillation, whose accuracy is ensured by the pair of         springs according to the invention;     -   increase the performance of oscillation of the selector when         said flat part is an oscillating selector;     -   increase the plurality of movements which can be assigned to the         needles so as to achieve a higher production flexibility, i.e.         so as to manufacture different types of fabrics with several         characteristics differing one from the other. 

1. A flat part for a knitting machine, wherein the knitting machine comprises a plurality of grooves (4), each housing one or more flat parts moving in translation and/or oscillating in said grooves (4), wherein the flat part comprises: a main flat body (100) and a pair of springs (20) protruding on opposed sides of the main flat body (100) and resting against opposed surfaces (4 a) of the respective groove (4); wherein each spring (20), when the flat part is inserted into the groove (4), pushes against the respective surface of the groove (4), so as to optimize oscillation of the flat part in said groove (4) and/or to stabilize the flat part in said groove (4).
 2. The flat part according to claim 1, wherein opposed lateral portions of the springs (20), configured for contacting the surfaces (4 a) of the groove (4), are located along an axis (Y-Y) basically orthogonal to the main flat body (100).
 3. The flat part according to claim 1, wherein each of the springs (20) comprises a bow-shaped plate whose convexity points outside the main flat body (100), wherein the bow-shaped plate is elastically deformable.
 4. The flat part according to claim 3, wherein the bow-shaped plate exhibits only one proximal end (21) joined to the main flat body (100).
 5. The flat part according to claim 4, wherein the main flat body (100) exhibits a through opening (23) and the springs (20) are located at said through opening (23).
 6. The flat part according to claim 5, wherein the proximal end (21) is joined to at least one edge of the through opening (23).
 7. The flat part according to claim 5, comprising a thin wall (102) thinner than a thickness of the main flat body (100), which is located in the through opening (23), wherein the proximal end (21) of each bow-shaped plate is joined to the thin wall (102).
 8. The flat part according to claim 6, wherein a distal end (22), opposed to the proximal end (21), of the bow-shaped plate is free.
 9. The flat part according to claim 18, wherein the proximal ends (21) and/or the distal ends (22) of each bow-shaped plate are basically located at a middle plane (P) of the main flat body (100).
 10. The flat part according to claim 1, wherein the springs (20) are symmetrical or basically symmetrical to a middle plane (P) of the main flat body (100).
 11. The flat part according to claim 1, wherein the springs (20) are configured for keeping the flat part on a median plane of the respective groove (4).
 12. The flat part according to claim 1, wherein only the springs (20) are configured for touching the opposed surfaces (4 a) of the respective groove (4), while the main flat body (100) lies at a distance from said surfaces (4 a).
 13. The flat part according to claim 1, wherein said flat part is chosen from the group comprising: a needle, a jack, a sub-needle, a selector (7), a pushing unit.
 14. A drive chain for a needle of a knitting machine, comprising at least one flat part in accordance with claim
 1. 15. A drive chain for a needle of a circular knitting machine, wherein the drive chain (5), once mounted to the circular knitting machine, is inserted into a respective longitudinal groove (4) of a needle-holding cylinder (2) of said machine, is located below a respective needle (3) and is operatively placed between the respective needle (3) and actuating cams (C) of said machine, said drive chain (5) comprising: a sub-needle (6) arranged below the needle (3) and engaged to the needle (3) so as to move axially in the respective longitudinal groove (4) together with said needle (3); wherein the sub-needle (6) comprises a moving butt (14) radially movable between an operating position, in which it is extracted from the needle-holding cylinder (2) so as to engage with respective first paths defined by first actuating cams (39) and cause the needle (3) to be activated, and a non-operating position, in which it is retracted in the needle-holding cylinder (2) so as not to engage with said first paths; a selector (7) partly located below the sub-needle (6) and partly beside the sub-needle (6), wherein the selector (7) is configured for oscillating between an active position, in which it pushes the moving butt (14) to the operating position, and a rest position, in which it allows the moving butt (14) to get back to the non-operating position, wherein the selector (7) is axially decoupled from the sub-needle (6) and from the needle (3) so that the needle (3) and the sub-needle (6) are never pushed or pulled axially by said selector (7); wherein the selector (7) is a flat part in accordance with claim
 1. 16. A knitting machine comprising a plurality of drive chains according to claim
 15. 17. A circular knitting machine, comprising: a needle-holding cylinder (2) having a plurality of longitudinal grooves (4) arranged around a central axis (X-X) of the needle-holding cylinder (2); a plurality of needles (3), each being housed in a respective longitudinal groove (4); actuating cams (C) arranged around the needle-holding cylinder (2); wherein said needle-holding cylinder (2) is movable with respect to the actuating cams (C) around the central axis (X-X) for causing or allowing the movement of the needles (3) along the longitudinal grooves (4) so as to enable stitch formation by said needles (3); a drive chain (5) for each needle (3) inserted into the respective longitudinal groove (4), located below the respective needle (3) and operatively placed between the respective needle (3) and said actuating cams (C); wherein said drive chain (5) is in accordance with claim
 15. 18. The flat part according to claim 1, wherein the main flat body (100) exhibits a through opening (23) and the springs (20) are located at said through opening (23).
 19. A knitting machine comprising a plurality of drive chains according to claim
 14. 20. A circular knitting machine, comprising: a needle-holding cylinder (2) having a plurality of longitudinal grooves (4) arranged around a central axis (X-X) of the needle-holding cylinder (2); a plurality of needles (3), each being housed in a respective longitudinal groove (4); actuating cams (C) arranged around the needle-holding cylinder (2); wherein said needle-holding cylinder (2) is movable with respect to the actuating cams (C) around the central axis (X-X) for causing or allowing the movement of the needles (3) along the longitudinal grooves (4) so as to enable stitch formation by said needles (3); a drive chain (5) for each needle (3) inserted into the respective longitudinal groove (4), located below the respective needle (3) and operatively placed between the respective needle (3) and said actuating cams (C); wherein said drive chain (5) is in accordance with claim
 14. 